Shared Flashcard Set

Details

Sensory and Motor Pathways
UCCS Bio 2010 Lykins- Exam 4, VAP 13.14-13.19
118
Anatomy
Undergraduate 1
12/17/2013

Additional Anatomy Flashcards

 


 

Cards

Term
Sensory pathways begin at _____ and end in the _____.
Definition
peripheral receptors
CNS, often in diencephalon &/or cerebral hemispheres
Term
sensation
Definition
info carried (much of it never reaches primary sensory cortex and our awareness)
Term
perception
Definition
conscious awareness of a sensation
Term
receptive field
Definition
area monitored by a single receptor; bigger = poorer ability to to localize a stimulus
Term
basic events along a sensory pathway
Definition
1. depolarization of a receptor- stimulus produces a graded change in transmembrane potential
2. a.p. generation
3. propagation over labeled line, info interpreted by CNS based on nature of axon it arrives on
Term
transduction
Definition
the conversion of a stimulus to change in membrane potential
Term
labeled line
Definition
axons carrying info about one type of stimulus (touch, pressure, temperature)
Term
Info goes from the sensory pathway to _____, and then to either the _____ or _____.
Definition
CNS processing
involuntary or voluntary motor pathway
Term
CNS processing part of the pathway
Definition
info is processed at every synapse along the labeled line, which may branch to distribute info to multiple nuclei and centers in the CNS
Term
involuntary motor pathway
Definition
immediate reflex response occurs, possibly even before sensations reach the cerebral cortex
Term
voluntary motor pathway
Definition
first perception occurs (only about 1% of arriving sensations), then the voluntary response occurs, which isn't immediate and can moderate, enhance, or supplement the relatively simple reflexive respone
Term
What are the simplest receptors? Describe them.
Definition
dendrites of sensory neurons
tips are free nerve endings so are not protected by accessory structures; can be stimulated by many different stimuli, so there is little receptor specificity
Term
What are the 4 main functional classifications of general sensory receptors?
Definition
nociceptors, thermoreceptors, chemoreceptors, and mechanoreceptors
Term
What are nociceptors and their two types?
Definition
pain receptors; free nerve endings with large receptive fields and broad sensitivity
Type A fibers and Type C fibers
Term
Type A fibers
Definition
nociceptors; myelinated axons that carry sensations of fast pain that very quickly reach the CNS (often triggering somatic reflexes) and are also relayed to the primary motor cortex for conscious attention; stimulus can be located to an area within a few cm
Term
Type C fibers
Definition
nociceptors that are slower, unmyelinated axons that carry sensations of slow pain that cause generalized activation of reticular formation and thalamus; only general idea of where the stimulus is located
Term
fast pain
Definition
prickling pain such as an injection or a deep cut that is felt by Type A fibers
Term
slow pain
Definition
burning, aching pain felt by Type C fibers
Term
thermoreceptors
Definition
temperature receptors that are free nerve endings located int he dermis, skeletal muscles, liver, and the hypothalamus
Term
Which type of thermoreceptor is there more of?
Definition
cold - 3-4x as many as warm, but the two have no structural difference at the cellular level
Term
chemoreceptors
Definition
respond to water-soluble and lipid-soluble substances that are dissolved in body fluids (interstitial fluid, plasma, and CSF)
Term
mechanoreceptors
Definition
sensitive to stimuli that distort the plasma membrane, which contain mechanically-gated ion channels that open/close to stretching, compression, twisting, etc.
Term
What types of mechanoreceptors are there?
Definition
proprioceptors, baroreceptors, and tactile receptors
Term
proprioceptors
Definition
the most structurally and functionally complex mechanoreceptors that monitor positions of joints and muscles
Term
baroreceptors
Definition
mechanoreceptors that detect pressure changes in walls of blood vessels and in portions of the digestive, reproductive, and urinary tracts
Term
tactile receptors
Definition
mechanoreceptors that provide sensations of touch, pressure, and vibration; two kinds- fine touch and pressure and crude touch and pressure
Term
What are the nature of the response classifications of the general sensory receptors?
Definition
tonic receptors and phasic receptors
Term
tonic receptors
Definition
always active, generate an a.p. at a frequency that reflects the background level of stimulation (ex. when stimulus increases or decreases, the rate of a.p. generation does too)
Term
phasic receptors
Definition
normally inactive, but become active for a short time in response to a change in the conditions they are monitoring
Term
adaptation
Definition
a decrease in sensitivity in the presence of a constant stimulus; peripheral and central
Term
peripheral adaptation
Definition
occurs when the level of receptor activity changes; responds strongly at first, then activity gradually decreases
Term
central adaptation
Definition
occurs along sensory pathways within the CNS; awareness of stimuli virtually disappears after a short time even though sensory neurons are quite active; generally involves inhibition of nuclei along a sensory pathway
Term
free nerve endings
Definition
branching tips of sensory neurons that aren't protected by accessory structures and are nonspecific; they are the most common receptors in the skin
Term
root hair plexus
Definition
nerve endings wherever hairs are located that monitor distortions and movements across the body surface, which distorts sensory dendrites and leads to a.p. production
Term
Which general sensory receptor is best at detecting initial contact and subsequent movements?
Definition
root hair plexus- adapts rapidly
Term
tactile discs
Definition
fine touch and pressure receptors that are extremely sensitive tonic receptors with very small receptive fields
Term
Merkel cells
Definition
large epithelial cells in the stratum basale of the skin that make close contact with the dendritic processes of a single myelinated afferent fiber
Term
tactile corpuscles
Definition
aka Meissner corpuscles; provide sensations of fine touch and pressure receptors and low-frequency vibration; quickly adapt to stimuli, are fairly large, and are surrounded by fibrous capsule that anchors it within the dermis
Term
Where are tactile corpuscles most abundant?
Definition
in the eyelids, lips, fingertips, nipples, and external genitalia
Term
What are the dendrites of tactile corpuscles like?
Definition
highly coiled and interwoven and are surrounded by modified Schwann cells
Term
lamellated corpuscles
Definition
aka pacinian corpuscles; sensitive to deep pressure; fast-adapting, which leads to them being most sensitive to pulsing or high-frequency vibrating stimuli
Term
What are the dendrites of lamellated corpuscles like?
Definition
single dendrite within a series of concentric collagen fibers and specialized fibroblasts that are separated by interstitial fluid and shield it from any other stimulation
Term
Where do lamellated corpuscles provide sensation to?
Definition
the dermis, mostly in the fingers, mammary glands, external genitalia, superficial and deep fascia, and in joint capsules
Term
Where do lamellated corpuscles provide information in?
Definition
visceral sensory info in mesenteries, pancreas, and walls of urethra and urinary bladder
Term
Ruffini corpuscles
Definition
sensitive to pressure and distortion of reticular dermis (deep); tonic and show little to no adaptation
Term
What are the dendrites of Ruffini corpuscles like?
Definition
network intertwined with a core of collagen fibers that are continuous with the dermis that are surrounded by a capsule; tension and distortion tugs and twists capsular fibers, causing stretching and compression of attached dendrites and altering activity in myelinated afferent fibers
Term
What are the three major somatic sensory pathways that carry information from the skin and musculature to the CNS?
Definition
spinothalamic, posterior column, spinocerebellar
Term
spinothalamic pathway
Definition
two tracts provide conscious sensations of crude touch, pressure, pain, and temperature
Term
Where do axons of first-order neurons synapse in the spinothalamic pathway?
Definition
they enter the spinal cord and synapse on second-order neurons within the posterior gray horn
Term
Where do axons of interneurons synapse in the spinothalamic pathway?
Definition
cross to opposite side of the spinal cord before ascending to the thalamus
Term
Where do third-order neurons synapse in the spinothalamic pathway?
Definition
primary sensory cortex from the thalamus
Term
anterior spinothalamic tracts
Definition
carry sensations of crude touch and pressure
Term
lateral spinothalamic tracts
Definition
carry pain and temperature sensations
Term
Where do second-order neurons synapse in the spinothalamic pathway?
Definition
in the ventral nuclei of the thalamus
Term
posterior column pathway
Definition
carries sensations of highly localized fine touch, pressure, vibration, and proprioception
Term
The posterior column pathway begins at _____ and ends at _____.
Definition
a peripheral receptor
primary sensory cortex
Term
Where do the sensory axons of the posterior column pathway go?
Definition
ascend in the fasciculus gracilis and cuneatus to the thalamus
Term
medial lemniscus
Definition
tract in the posterior column pathway leading from the nucleus gracilis and nucleus cuneatus to the thalamus
Term
spinocerebellar pathway
Definition
sends proprioceptive info about position of skeletal muscles, tendons, and joints to the cerebellum
Term
Posterior axons of the spinocerebellar pathway...
Definition
don't cross over to the opposite side of the spinal cord, they reach the cerebellar cortex via the inferior cerebellar peduncles of the same side, mostly on posterior tracts
Term
Anterior tracts of the spinocerebellar pathway
Definition
are dominated by axons that have crossed over
Term
The somatic motor pathways always involve
Definition
at least 2 motor neurons (upper and lower)
Term
What are the 3 major somatic motor pathways?
Definition
corticospinal, medial, and lateral
Term
upper motor neurons
Definition
cell body lies in a CNS processing center
Term
lower motor neurons
Definition
cell body lies in a nucleus of the brain stem or spinal cord
Term
Where does the upper motor neuron synapse?
Definition
on the lower motor neuron, which innervates a single motor unit in a skeletal muscle
Term
motor homunculus
Definition
functional map of the cortical areas in a specific region of the bod; motor area devoted to a specific region of the cortex is proportional to the number of motor units innervated and the degree of fine motor control available
Term
sensory homunculus
Definition
sensory map of the primary sensory cortex; areas of sensory cortex devoted to particular body regions is proportional to the number of sensory receptors it contains
Term
corticospinal pathway
Definition
aka pyramidal system; voluntary control over skeletal muscles
Term
The corticospinal pathway begins at _____.
Definition
pyramidal cells of the primary motor cortex
Term
Axons of the upper motor neurons of the corticospinal pathway descend into _____ to synapse on _____.
Definition
the brain stem and spinal cord
lower motor neurons that control skeletal muscles
Term
What happens along the length of the pyramids in the corticospinal pathway?
Definition
85% of the axons of the pathway cross the midline to enter the lateral corticospinal tracts
Term
Axons in the corticobulbar tracts of the corticospinal pathway synapse on
Definition
lower motor neurons in the motor nuclei of the cranial nerves
Term
corticobulbar tracts
Definition
provide conscious control over skeletal muscles that move the eye, jaw, face, and some of the neck and pharynx
Term
Descending axons of corticospinal tracts of the corticospinal pathway are visible
Definition
along the ventral surface of the medulla oblongata as thick bands called the pyramids
Term
anterior corticospinal tracts
Definition
the 15% of corticospinal axons that descend uncrossed
Term
medial pathway
Definition
somatic motor commands issued by several centers in the cerebrum, diencephalon, and brain stem that help control gross motor movements of the neck, trunk, and proximal limb muscles (result of subconscious processing)
Term
What are the nuclei of the medial pathway?
Definition
superior and inferior colliculi, reticular formation, vestibular nucleus; they are where the upper motor neurons are located
Term
reticulospinal tracts
Definition
part of the medial pathway; contain axons of upper motor neurons in the reticular formation
Term
What is the reticular formation's role in the pathways?
Definition
receives input from almost every ascending and descending pathway has interconnections with the cerebrum, cerebellum, and brain stem nuclei
Term
vestibulospinal tracts
Definition
receive sensory info from inner ear about the position and movement of the head; respond to change in orientation of the head by issuing motor commands that alter muscle tone and position of the neck, eyes, head, and limbs
Term
tectospinal tracts
Definition
contain axons of upper motor neurons in the superior and inferior colliculi of the midbrain that direct reflexive change in position of the head, neck, and upper limbs
Term
lateral pathway
Definition
somatic motor commands issued from several centers in the cerebrum, diencephalon, and brain stem as a result of processing performed at the subconscious level
Term
The lateral pathway controls what?
Definition
distal limb muscles that perform precise movements
Term
What is the primary nucleus of the lateral pathway?
Definition
red nucleus- receives info from the cerebrum and cerebellum to adjust distal limb muscles and background muscle tone
Term
What are in the red nucleus?
Definition
upper motor neurons, whose axons cross to opposite sides of the brain and descend into the spinal cord in rubrospinal tracts that are small and extend only to the cervical spinal cord
Term
What are the tracts of the spinothalamic pathway?
Definition
anterior spinothalamic tracts, lateral spinothalamic tracts; importantly there are the three orders of neurons
Term
What are the tracts of the posterior column pathway?
Definition
medial lemniscus
Term
What are the tracts of the spinocerebellar pathway?
Definition
posterior spinocerebellar tracts and anterior spinocerebellar tracts,
Term
What are the tracts of the corticospinal pathway?
Definition
corticobulbar tracts, corticospinal tracts (pyramids), anterior corticospinal tracts, and lateral corticospinal tracts
Term
What are the tracts of the medial pathway?
Definition
reticulospinal tracts, vestibulospinal tracts, and tectospinal tracts
Term
What are the tracts of the lateral pathway?
Definition
rubrospinal tracts; also has the red nucleus
Term
What do the basal nuclei do in somatic motor control?
Definition
modify voluntary and reflexive motor patterns at the subconscious level
Term
What are the two main pathways for subconscious motor commands?
Definition
medial and lateral pathways
Term
What are the roles of the brain stem and spinal cord in somatic motor control?
Definition
control simple cranial and spinal reflexes
Term
What are the roles of the pons and medulla oblongata in somatic motor control?
Definition
control balance reflexes and more complex respiratory reflexes
Term
What are the roles of the hypothalamus in somatic motor control?
Definition
controls reflex motor patterns related to eating, drinking, and sexual activity; modifies respiratory reflexes
Term
What are the roles of the thalamus and midbrain in somatic motor control?
Definition
control reflexes in response to visual and auditory stimuli
Term
What are the roles of the cerebral cortex in somatic motor control?
Definition
plans and initiates voluntary motor activity
Term
What are the roles of the cerebellum in somatic motor control?
Definition
coordinates complex motor patterns through feedback loops involving the cerebral cortex and basal nuclei as well as the medial and lateral pathways
Term
How do we prepare for a movement?
Definition
info is relayed from the frontal lobes to the motor association areas which relay it to the cerebellum and the basal nuclei
Term
How do we perform a movement?
Definition
the motor association areas send instructions to the primary motor cortex
Term
What modify the commands as we perform a movement?
Definition
feedback from basal nuclei and the cerebellum; output along the medial and lateral pathways directs involuntary adjustments in position and muscle tone
Term
How do the basal nuclei adjust our movement patterns?
Definition
1. they alter sensitivity of pyramidal cells to adjust the output along the corticospinal tract
2. they change the excitatory or inhibitory output of the medial and lateral pathways
Term
Damage to the primary motor cortex can lead to
Definition
loss of ability to exert find control over skeletal muscles
Term
How do the basal nuclei and cerebellum help if the primary motor cortex is damaged?
Definition
They can still control some voluntary movements, but they're awkward movements still; the cerebellum can't fine tune movements, but it can help a person stand, balance, and walk
Term
Nervous system disorders may result from
Definition
problems with neurons, pathways, or a combination of the two
Term
What causes referred pain?
Definition
strong visceral pain sensations arriving at a segment of the spinal cord can stimulate interneurons that are a par of the spinothalamic pathway, which causes stimulation of the primary sensory cortex
Term
Parkinson disease
Definition
neurons of the substantia nigra are damaged or secrete less dopamine, and the basal nuclei become more active, which leads to increase in skeletal muscle tone and rigidity and stiffness
Term
rabies
Definition
a bite injects the virus into peripheral tissues, where virus particles quickly enter synaptic knobs, and then retrograde flow carries it into the CNS
Term
cerebral palsy (CP)
Definition
a number of disorders that affect voluntary motor performance; they appear during infancy or childhood and persist all of life; cause may be trauma from birth, maternal exposure to drugs, or a genetic defect causing improper development of motor pathways
Term
amyotrophic lateral sclerosis (ALS)
Definition
aka Lou Gehrig disease; a progressive, degenerative disorder that affects motor neurons (upper and lower) in the spinal cord, brain stem, and cerebral hemispheres that causes atrophy of the associated skeletal muscles; possibly due to a defect in axonal transport;
Term
Alzheimer disease
Definition
progressive disorder characterized by the loss of higher-order cerebral functions; causes intra and extracellular abnormalities in the brain regions such as the hippocampus and other memory processing areas
Term
Alzheimer disease is the most common cause of what disorder?
Definition
senile dementia (aka senility)
Term
When does Alzheimer disease normally come on, and what are its demographics?
Definition
age 50-60 or older, but it can affect younger people; 2 million people in US have it, including 15% of those over 65 and 1/2 of those over 85; causes 100000 deaths every year
Term
multiple sclerosis (MS)
Definition
recurrent incidents of demyelination that affects axons in the optic nerve, brain, and spinal cord
Term
What are the symptoms of MS?
Definition
partial loss of vision and problems with speech, balance, and general motor coordination including bowel and bladder control
Term
How does MS work?
Definition
it's progressive in 1/3 of cases, progressing after each incident; the 1st attack is usually among 30-40 year olds and is 1.5x more likely in women
Supporting users have an ad free experience!